The present inventions relate generally to locating mobile stations, and more particularly to locating satellite positioning system enabled mobile stations.
Locating cellular telephone handsets in cellular communication networks based on a satellite positioning system, for example the Navigation System with Time and Range (NAVSTAR) global positioning system (GPS), is one approach likely to be implemented for supporting enhanced emergency 911 (E-911) services, which will soon be mandatory in the United States of America.
Market driven forces are also motivating communications equipment manufacturers and service providers to more quickly and accurately locate cellular telephone handsets and other mobile stations, for example to provide promotional and fee based value-added services. Satellite positioning system based positioning will likely be among the contenders for many of these market opportunities.
Satellite positioning system enabled mobile stations generally require a satellite signal receiver interface, which draws power in some proportion to the rate at which satellite signals are received and location fixes are generated. Satellite positioning system based positioning schemes will thus reduce standby and talk time in battery-operated mobile stations, for example cellular telephone handsets.
Additionally, there will likely be service fees associated with at least some satellite positioning system based positioning schemes, for example those utilizing terrestrial network-assistance.
Reducing the frequency or rate at which the cellular handset generates and updates satellite positioning system based location fixes, for example, to conserve battery power and reduce costs associated therewith, generally increases the time required to obtain a position fix. In some applications, however, a substantial delay in the generation of a location fix is undesirable or unacceptable, for example in E-911 applications where the caller is in imminent danger, or where the mobile station is moving at a high rate of speed and will have changed its position significantly by the time a position fix is obtained.
The various aspects, features and advantages of the present inventions will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following detailed description of the inventions in conjunction with the accompanying drawings, which are described below.